Gangliosides have been implicated as receptor components for thyrotropin (TSH), toxins, and interferon. Monoclonal antibodies to gangliosides offers an experimental approach to examine the role of gangliosides in cellular recognition and the biological response to ligands. A subset of the monoclonal antibodies, prepared to the solubilized TSH receptor components that block or mimic some of the effects of TSH, has been found to interact with gangliosides. Monoclonal antibodies have independently been developed to specific gangliosides, and their effects on cell growth and interferon bioactivity have been determined. Studies in this laboratory have been aimed at evaluating the hypothesis that a primary action of TSH, tetanus toxin, and interferon is an effect on the membrane that results in altered ion fluxes across the membrane. These studies continue to support this view and have further defined specific mechanisms by which tetanus toxin and interferon affect the electrochemical ion gradient. Recent studies have characterized iodide transport mechanisms in thyroid cells in culture, as well as described TSH-induced alterations in iodide flux.